The invention is directed to dredging, and, more particularly, to a closed circuit dredging system which circulates the water removed from a dredging area back to the dredging apparatus to mix with the dredged solids so as to prevent clogging of the dredging apparatus.
Dredging is commonly used to remove accumulated sediment from waterways in an effort to maintain them open. For example, dredging is conducted in waterways such as rivers which support shipping when the vessel channels become diminished due to the presence of sediment deposits.
Dredging is also important in areas where agriculture is practiced. In agricultural areas, the runoff of chemicals such as plant fertilizers into the waterways promotes the rapid growth of undesirable vegetation. The growth of vegetation can be so severe in some instances, that the effected waterways are restricted in a short period of time. In such environments, dredging must be performed periodically to prevent closure of the waterways from occurring.
Although the known dredging systems are capable of removing sediment and vegetation from waterways, they also tend to detrimentally affect the surrounding environment. The known dredging systems having conventional dredging scoops have the disadvantage of being unable to efficiently remove relatively lightweight sediment from waterways due to the sediment suspending in the water. To overcome this problem, dredge pumps have been used to draw the sediment out of the waterways. The dredge pumps, however, tend to become clogged by the lightweight sediment. Consequently, the known dredging apparatuses have been unable to operate continuously for extended periods of time without having to periodically discontinue the dredging operation to remove the clogging material.
The problem of clogging has caused the known dredging apparatuses to significantly increase the turbidity of the waterways by disturbing a large amount of sediment during dredging. Consequently, vegetation has been prevented from receiving an adequate amount of sunlight. After the life-supporting vegetation dies, the fish and wildlife which rely on the vegetation for oxygen, cover and food, are forced to seek supporting vegetation in other areas. As a result of the plants and animals leaving the dredged area, ecosystems have been left adversely affected.
The increased turbidity created in the waterways by the known dredging apparatuses has also made it difficult for the operator to visually monitor the progress of the dredging operation. Consequently, the known dredging systems have been restricted by their inefficiency.